1. Electric Field Physics Gillis

2. Analogy The electric field is the space around an electrical charge just like a gravitational field is the space around a mass.

3. Electric Field • Space around a charge.

4. What is the difference?

5. Electric Field Vector, E • E = F/ qo • qo , positive test charge • E is a vector quantity • Unit: N/C • E is analogous to the gravitational field, g, where g=F/m

6. Example 1 • A charge of 3µC is used to test the electric field of a central charge that causes a force of 800N. What is the magnitude of the electric field? • E= 800/3x106 • Answer: 2.7 x108 N/C

7. Electric Field http://higheredbcs.wiley.com/legacy/college/halliday/0471320005/simulations6e/index.htm?newwindow=true

8. Electric Field Lines

9. Electric Field Lines of two Positive Charges

10. Electric Field Lines • Lines that indicate the strength and direction of the electric field. • The more dense the lines, the stronger the field. • Electric field vectors are tangent to the curve. • Simulation http://online.cctt.org/physicslab/content/applets/pointcharges/elefi_z.htm

11. Conductors and Electric Fields (under electrostatic conditions) • “The electric field is zero inside a charged conductor”. • “Excess charge on an isolated conductor resides on the surface”. • “Excess charge accumulates on sharp points”. • Electric field lines meet the conductor perpendicular to the surface of the conductor.

12. Shielding • The electric field is zero inside a charged conductor.

13. Which field is stronger? • A B

14. Electric Field for a Point Charge Using E=F/qo and Coulomb’s Law prove: E = k Q ______ d2 where Q is the central charge.

15. Example 2 • A test charge of +3µC is located 5m to the east of a -4µC charge. • A) Find the electric force felt by the test charge. • B) Find the electric field at that location. • Answer: 4.32x10-3 N, 1.44 x 103 N/C along the –x axis.